The present invention relates to arrangements for the prevention or minimisation of over-pressures due to sudden interruptions in the flow of a compressible fluid which are caused by an obturator such as an electrical valve which is situated along a main gas pipe, and particularly such arrangements which consist of a pressure regulator and reducer mounted on the said main pipe upstream of the obturator and the response time of which is longer than that of the said obturator, a venturi which communicates with that section of the main pipe which is situated between the obturator and the regulator and reducer, and a buffer reservoir which is in permanent communication with the said section of main pipe via the venturi. Hereinafter such arrangements will be referred to as "arrangements of the kind described".
Arrangements of the kind described are set forth in French Pat. No. 73.17815 filed May 16 1973 and enable the maximum limits between which the pressure in the fluid varies when such obturators open and close to be kept to a level lower than that at which the safety devices trigger. These safety devices are thus prevented from triggering at the wrong time and the general functioning of the installation is thereby substantially improved.
However, to put an arrangement of the kind described into practice it was necessary to employ and thus to connect together a number of additional valves and pipes and this led to a regulation system which was rather complicated to produce and fit and to a corresponding increase in the cost of the system.
In fact, in the specific embodiment fully described in the aforementioned French Pat. No. 73.17815, the venturi is mounted as a by-pass to the pressure regulator and reducer, with the result that it is necessary to provide, upstream of the venturi, a cut-off valve which shuts off the connection between the said venturi and the main pipe upstream of the pressure reducer and regulator when the obturator is closed.
It is an object of the invention to improve the said known arrangement of the kind described in such a way as to simplify its design, operation and fitting.